Coated papers which are widely used as printing papers have been conventionally manufactured by coating base papers with a composition mainly consisting of a pigment such as clay and calcium carbonate and binders such as latex and starch. With remarkable development in the printing technology of recent years exemplified by printing at a higher speed, with higher resolution and/or in more colors, higher level printability has come to be required for coated papers. In particular, the following three properties are strongly required: (i) ink receptivity which means how well ink takes on the paper when the printing is carried out; (ii) resistance to the damping water which is applied on the paper in the offset printing; and (iii) resistance to blister which may occur as the ink dries in the webb offset printing.
Various types of resins have been developed so as to provide coated papers with the above-mentioned properties necessary for good printing. A polyalkylenepolyamine-urea-formaldehyde resin is one of such resins and combinationed use of a polyalkylenepolyamine-urea-formaldehyde resin and a dialdehyde is suggested for this purpose (see Japanese Laid-open publication No. 51-121041, for example). We have also tried combinationed use of a polyalkylenepolyamine-urea-aldehyde resin and an amine-epihalohydrin resin by mixing and/or reacting these resins.
These efforts are, however, not successful in achieving a well-balanced improvement in the above-mentioned three properties (ink receptivity, water resistance and blister resistance) and, therefore, such an improved resin as satisfies the requirements is desired. Especially it is very difficult to improve both the ink receptivity and the water resistance in a good balance. For example, when the ink receptivity is tried to be enhanced by making the coating layer more permeable to the damping water, the water resistance thereof is impaired and the phenomenon that the surface of the coating layer is partially taken off by the inking roller (so-called "wet pick") is more liable to occur.